Tissue enzyme levels as indices of protein status in sheep

Abstract

1. An investigation was made to determine the value of tissue enzymes as indices of protein nutrition.2. Sheep were given a reduced protein intake for 6 weeks, whereupon some were given a protein supplement for 1 week and then the sheep were refed their initial diet. In the first experiment sheep were taken from pasture and given a reduced protein intake for 6 weeks whereupon some were given a protein supplement for 1 week and then all the sheep were grazed on pasture. In the second experiment sheep were fed on lucerne (Medicago sativa) chaffad lib.in place of grazing before and after the period of reduced protein intake during which one group was also fed on molasses. Again, another group was given a protein supplement for 1 week after 6 weeks on the reduced protein intake.3. As a result of reduced protein intake there were significant (P< 0.01) changes in the liver in the content of DNA, protein: DNA, arginine synthetase (combined activity of argininosuccinate synthetase (EC6.3.4.5) and argininosuccinate lyase (EC4.3.2.1)), aspartic aminotransferase (EC2.6.1.1), glutamic dehydrogenase (EC1.4.1.2), arginase (EC6.5.3.1) and tyrosine aminotransferase (EC2.6.1.5).4. There were few consistent changes in muscle in the levels of DNA, protein:DNA, creatine kinase (EC2.7.3.2) and aspartic aminotransferase.5. The feeding of molasses to one group tended to reduce the change in DNA level but still resulted in significant changes in the enzymes.6. It is suggested that the levels of arginine synthetase, aspartic aminotransferase and DNA in liver could be useful indices of protein status.